C Program to Find Nearest Sibling of a Node in Tree

This C Program Finds the Nearest Sibling of a Node in a Tree.

Here is source code of the C Program to Find the Nearest Sibling of a Node in a Tree. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

```
/*
```

 * C Program to Find the Nearest Sibling of a Node in a Tree

```
 */ 
```
```
#include <stdio.h>
```
```
#include <stdlib.h>
```
```
 
```
```
struct btnode
```
```
{
```
```
    int value;
```
```
    struct btnode *l;
```
```
    struct btnode *r;
```
```
}*root = NULL;
```
```
 
```
```
// Function Prototype
```
```
void printout(struct btnode*);
```
```
struct btnode* newnode(int);
```
```
void find(struct btnode *, int);
```

void find_sibling(struct btnode *, int);

```
 
```
```
void main()
```
```
{
```
```
    int data, res = 0;
```
```
 
```
```
    root = newnode(50);
```
```
    root->l = newnode(20);
```
```
    root->r = newnode(30);
```
```
    root->l->l = newnode(70);
```
```
    root->l->r = newnode(80);
```
```
    root->l->r->r = newnode(60);
```
```
    root->l->l->l = newnode(10);
```
```
    root->l->l->r = newnode(40);
```
```
    printf("tree elements are\n");
```
```
    printout(root);
```
```
    printf("\nenter element to find");
```
```
    scanf("%d", &data);
```
```
    if (root->value == data)
```

        printf("--NO SIBLING FOR ROOT NODE--\n");

```
    else
```
```
    {
```
```
        find(root,data);
```
```
    }
```
```
}
```
```
 
```
```
// Create a node
```
```
struct btnode* newnode(int value)
```
```
{
```

    struct btnode* node = (struct btnode*)malloc(sizeof(struct btnode));

```
    node->value = value;
```
```
    node->l = NULL;
```
```
    node->r = NULL;
```
```
    return(node);
```
```
}
```
```
 
```
```
// to display the tree
```
```
void printout(struct btnode *tree)
```
```
{
```
```
    if (tree->l)
```
```
        printout(tree->l);
```
```
    printf("%d\t", tree->value);
```
```
    if (tree->r)
```
```
        printout(tree->r);
```
```
}
```
```
 
```
```
// To find node in a tree
```

void find(struct btnode *tree, int data)

```
{
```
```
    static int count = 0;
```
```
    struct btnode *ptr = root;
```
```
    int i;
```
```
 
```
```
    if (tree->l || tree->r)
```
```
    {
```
```
        if (tree->l->value == data)
```
```
            find_sibling(tree, 1);
```

        else if (tree->r->value == data)

```
            find_sibling(tree, 0);
```
```
        else
```
```
        {
```
```
            find(tree->l, data);
```
```
            find(tree->r, data);
```
```
        }
```
```
    }
```
```
}
```
```
 
```
```
// To find sibling of a node in a tree
```

void find_sibling(struct btnode *tree,int side)

```
{
```
```
    if (side == 1 && tree->r != NULL)
```
```
    {
```

        printf("--------SIBLING FOUND---------\n");

```
        printf("%d\n", tree->r->value);
```
```
    }
```

    else if (side == 0 && tree->l != NULL)

```
    {
```

        printf("--------SIBLING FOUND---------\n");

```
        printf("%d\n", tree->l->value);
```
```
    }
```
```
}
```

$ gcc tree13.c
$ a.out
tree elements are
10      70      40      20      80      60      50      30
enter element to find 20
--------SIBLING FOUND---------
30
$ a.out
tree elements are
10      70      40      20      80      60      50      30
enter element to find 10
--------SIBLING FOUND---------
40
$ gcc tree13.c
$ a.out
tree elements are
10      70      40      20      80      60      50      30
enter element to find 30
--------SIBLING FOUND---------
20

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